1. Field of the Invention
This invention relates to network communication systems and in particular to a communication system including a combination of a Wide Area Network and a Local Area Network.
2. Related Art
Today, many businesses and individuals use computers connected by networks for communication. These computers may be mobile computers with wireless modems. These mobile computers are empowered by mobile data networks and wireless networks, which connect the mobile computers to each other and to various databases. Two primary kinds of networks that provide connectivity to these mobile computers are Local Area Network (LAN) and Wide Area Network (WAN).
A wireless LAN carries high-speed traffic by utilizing a random access technique such as Carrier-Sense Multiple Access (CSMA). An advantage of a wireless LAN is that once installed, there is no significant charge for accessing the LAN. A wireless LAN, however, has a disadvantage of not being able to readily support real time transfer of high-bandwidth data. Furthermore, a wireless LAN is accessible only from a limited geographical coverage area. A LAN is usually used to provide islands of coverage within an office, a building, or a campus. A consequence of the limited cell size is that a wireless LAN is not appropriate for access from a high-speed mobile unit. If a mobile unit moves quickly through many cells, the network is not able to keep track of the mobile unit.
A wireless WAN, unlike a LAN, supports real time data transfers and provides a greater guaranteed bandwidth. Furthermore, a wireless WAN provides ubiquitous coverage so a user of a wireless WAN can expect to be able to access the network from almost anywhere. As a result of the sufficiently large cell size, a wireless WAN can support high-speed mobility. Even a mobile unit moving at a high speed does not rapidly traverse different cells because each cell covers a large area. A wireless WAN, however, has a disadvantage of being expensive to access because it is accessed through a mobile data base station (e.g., CDMA, CDPD, GSM). Accessing a WAN wirelessly results in airtime charges, which could make frequent access for long periods of time expensive.
Since a wireless LAN and a wireless WAN have different sets of advantages and disadvantages, a system that allows a user to take advantage of the strengths of each network without suffering the disadvantages is needed.